feat(ivy): support enum values in static resolution (angular#25619)

This commit adds support for enumeration values. An enumeration value
is now a first-class return value of the resolver, which provides both
a Reference to the enum type itself and the name of the value from that
enum. Resolving an enum itself returns a Map<string, EnumValue>.

PR Close angular#25619

Author: alxhub

packages/compiler-cli/src/ngtsc/metadata/index.ts

@@ -9,4 +9,4 @@
 /// <reference types="node" />
 
 export {TypeScriptReflectionHost, filterToMembersWithDecorator, findMember, reflectObjectLiteral, reflectTypeEntityToDeclaration} from './src/reflector';
-export {AbsoluteReference, ImportMode, Reference, ResolvedReference, ResolvedValue, isDynamicValue, staticallyResolve} from './src/resolver';
+export {AbsoluteReference, EnumValue, ImportMode, Reference, ResolvedReference, ResolvedValue, isDynamicValue, staticallyResolve} from './src/resolver';

packages/compiler-cli/src/ngtsc/metadata/src/resolver.ts

@@ -53,7 +53,7 @@ export function isDynamicValue(value: any): value is DynamicValue {
  * non-primitive value, or a special `DynamicValue` type which indicates the value was not
  * available statically.
  */
-export type ResolvedValue = number | boolean | string | null | undefined | Reference |
+export type ResolvedValue = number | boolean | string | null | undefined | Reference | EnumValue |
     ResolvedValueArray | ResolvedValueMap | DynamicValue;
 
 /**
@@ -72,6 +72,15 @@ export interface ResolvedValueArray extends Array<ResolvedValue> {}
  * `ResolvedValue`.
  */ export interface ResolvedValueMap extends Map<string, ResolvedValue> {}
 
+/**
+ * A value member of an enumeration.
+ *
+ * Contains a `Reference` to the enumeration itself, and the name of the referenced member.
+ */
+export class EnumValue {
+  constructor(readonly enumRef: Reference<ts.EnumDeclaration>, readonly name: string) {}
+}
+
 /**
  * Tracks the scope of a function body, which includes `ResolvedValue`s for the parameters of that
  * body.
@@ -438,13 +447,27 @@ class StaticInterpreter {
       return context.scope.get(node) !;
     } else if (ts.isExportAssignment(node)) {
       return this.visitExpression(node.expression, context);
+    } else if (ts.isEnumDeclaration(node)) {
+      return this.visitEnumDeclaration(node, context);
     } else if (ts.isSourceFile(node)) {
       return this.visitSourceFile(node, context);
     } else {
       return this.getReference(node, context);
     }
   }
 
+  private visitEnumDeclaration(node: ts.EnumDeclaration, context: Context): ResolvedValue {
+    const enumRef = this.getReference(node, context) as Reference<ts.EnumDeclaration>;
+    const map = new Map<string, EnumValue>();
+    node.members.forEach(member => {
+      const name = this.stringNameFromPropertyName(member.name, context);
+      if (name !== undefined) {
+        map.set(name, new EnumValue(enumRef, name));
+      }
+    });
+    return map;
+  }
+
   private visitElementAccessExpression(node: ts.ElementAccessExpression, context: Context):
       ResolvedValue {
     const lhs = this.visitExpression(node.expression, context);
@@ -689,6 +712,8 @@ function literal(value: ResolvedValue): any {
 function identifierOfDeclaration(decl: ts.Declaration): ts.Identifier|undefined {
   if (ts.isClassDeclaration(decl)) {
     return decl.name;
+  } else if (ts.isEnumDeclaration(decl)) {
+    return decl.name;
   } else if (ts.isFunctionDeclaration(decl)) {
     return decl.name;
   } else if (ts.isVariableDeclaration(decl) && ts.isIdentifier(decl.name)) {

packages/compiler-cli/src/ngtsc/metadata/test/resolver_spec.ts

@@ -11,7 +11,7 @@ import * as ts from 'typescript';
 
 import {TypeScriptReflectionHost} from '..';
 import {getDeclaration, makeProgram} from '../../testing/in_memory_typescript';
-import {AbsoluteReference, Reference, ResolvedValue, staticallyResolve} from '../src/resolver';
+import {AbsoluteReference, EnumValue, Reference, ResolvedValue, staticallyResolve} from '../src/resolver';
 
 function makeSimpleProgram(contents: string): ts.Program {
   return makeProgram([{name: 'entry.ts', contents}]).program;
@@ -265,4 +265,23 @@ describe('ngtsc metadata', () => {
 
   it('template expressions work',
      () => { expect(evaluate('const a = 2, b = 4;', '`1${a}3${b}5`')).toEqual('12345'); });
+
+  it('enum resolution works', () => {
+    const result = evaluate(
+        `
+      enum Foo {
+        A,
+        B,
+        C,
+      }
+
+      const r = Foo.B;
+    `,
+        'r');
+    if (!(result instanceof EnumValue)) {
+      return fail(`result is not an EnumValue`);
+    }
+    expect(result.enumRef.node.name.text).toBe('Foo');
+    expect(result.name).toBe('B');
+  });
 });